| → in their affinities they 1860 1861 1866 1869 1872 |
| they 1859 |
|
| → both of which 1866 1869 |
| which 1859 1860 1861 |
| both 1872 |
|
| → each existed first as a 1866 1869 1872 |
| all species first existed as 1859 1860 1861 |
|
| → within each class tend 1861 1866 1869 1872 |
| tend 1859 1860 |
|
|
present many varieties; for where the manufactory of species has been active, we might expect, as a general rule, to find it still in action; and this is the case if varieties be incipient species. Moreover, the species of the larger genera, which afford the
number of varieties or incipient species, retain to a certain degree the character of varieties; for they differ from each other by a less amount of difference than do the species of smaller genera. The closely allied species also of the larger genera apparently have restricted ranges, and
→in their affinities they
are clustered in little groups round other species— in
→both of which
respects
varieties. These are strange relations on the view
each species
independently created, but are intelligible if
→each existed first as a
|
|
| As each species tends by its geometrical
of reproduction to increase inordinately in number; and as the modified descendants of each species will be enabled to increase by
much
as they become
diversified in habits and structure, so as to be
to seize on many and widely different places in the economy of nature, there will be a constant tendency in natural selection to preserve the most divergent offspring of any one species.
during a long-continued course of modification, the slight
characteristic of varieties of the same species, tend to be augmented into the greater differences characteristic of
of the same genus. New and improved varieties will inevitably supplant and exterminate the older, less
and intermediate varieties; and thus species are rendered to a large extent defined and distinct objects. Dominant species belonging to the larger groups
→within each class tend
to give birth to new and dominant forms; so that each large group tends to become still larger, and at the same time more divergent in character.
|
